The World Countries Tree visualizes the hierarchical structure of global geography, from continents through subregions down to individual countries, using a horizontal tree layout rendered as SVG. It employs D3 v5’s `tree` and `hierarchy` functions to compute the layout, `linkHorizontal` for curved connector paths, and a zoom behavior for interactive panning and scaling. Font sizes decrease with tree depth, and the dataset is loaded from a local `data.json` file.